1. Field of the Invention
this invention relates to an internal-diameter tube cutter which cuts by means of a flailing action.
2. Description of the Prior Art
Internal-diameter tube cutters are generally known in the prior art. One of the most common types of such cutters includes a pair of opposing blades which are outwardly extendable by means of a cam. In operation, this type of cutter is slid into the tube to be cut, and the blade-extending cam is forcefully wedged through cam slots in the blades while the cutter is rotated. The cutting action of such cutters is similar to that of an ordinary household can opener, wherein the workpiece is rotated relative to the blade while a steady pressure causes the blade to slice into the wall of the tube.
While such internal-diameter tube cutters provide statisfactory results in many applications, certian problems may arise when tube cutters of this design are used to cut sample tubes in nuclear steam generators. For example, if the internal diameter of the tube to be sampled has been dented around the area of the generator support plates, or internally sleeved to prevent a leak condition from arising in the tube, it may not be possible to slide a conventional, internal-diameter tube cutter through the restrictions in the tube caused by either such dents or sleeves. If one attempts to solve this problem by merely reducing the width of this kind of tube cutter so it can slide through such restrictions, the mechanical strength of the cutter may be diminished to the point where it breaks down or wears out after a few tube cuts. Still another problem associated with such internal-diameter tube cutters is the relatively long period of time it takes to penetrate the walls of the tube with such a cutter. This problem is particularly acute when tube samples are being cut from a nuclear steam generator. In such a radioactive environment, the longer such a tube cutting process requires, the more radiation the maintenance personnel performing such operations will be exposed to.
Accordingly, there is a need for an internal-diameter tube cutter which is small enough in cross-section to easily slide past tube restrictions caused by either denting or sleeving, but mechanically strong enough so that it is capable of cutting through the walls of the tube without breaking or excessive wear. In addition to being small and durable, it would also be desirable if such a tube cutter were capable of rapidly penetrating the wall of the tube sought to be cut, in order to minimize the amount of radiation which maintenance personnel in nuclear steam generators are exposed to. Finally, it would be desirable if such a tube cutter were simple in design, and easy and inexpensive to manufacture and to use.